This invention relates generally to aquatic weed cutting machines. More particularly, this invention pertains to boat-mounted machines for cutting aquatic plants growing in bodies of water.
The overgrowth of aquatic plants in freshwater lakes often results in the deprivation of subsurface sunshine, the depletion of dissolved oxygen, and contributes to the eutrophication of the water body, particularly in the die-off which occurs in the autumn of the year. Nutrients which have been deposited in the sediments over a long time period are re-introduced to the water body, resulting in over-fertilization.
Often, over-growth of aquatic weeds decreases the viability of the fish population, limiting the water surface area available for use by waterfowl and anglers, swimmers and waterskiers.
Eurasian watermilfoil is a particularly troublesome weed, having a high reproduction rate which enables it to completely take over a body of water in a few years. Other plants are rapidly displaced, and the water body loses much of its value as a resource for wildlife and recreational values, e.g. boating, fishing and swimming.
While the introduction of copper compounds into the water body has been used to limit plant growth, its general application is considered not acceptable for ecological reasons.
Various types of apparatus have been devised for cutting aquatic weeds. For example, U.S. Pat. No. 1,200,096 of Firman discloses a kelp harvester using cutter blades mounted on a pair of spinning horizontal circular disks.
U.S. Pat. No. 2,317,367 of Foerster describes a submarine weed cutter using a straight saw blade suspended between the ends of a cable, by which the blade is reciprocally moved.
A U.S. Pat. No. 4,205,507 of McClure discloses a weed cutter with a cutter bar comprising two elongate members. Each member has a plurality of teeth, and relative reciprocating movement of the members provides a cutting action therebetween.
In U.S. Pat. Nos. 4,328,658, 4,815,260 and 4,942,722, Desrosiers et al. show a weed harvester which is basically a multi-strand cable which is drawn through a weedy area and continuously twisted. The twisting action wraps weeds around the cable, and cable movement wrenches the weeds from the ground, drawing them to the drive mechanism. The apparatus is not a cutter.
In U.S. Pat. Nos. 4,885,902 and 5,189,867, Schmidt describes another aquatic vegetation cutter using a cutter bar with two reciprocating blade assemblies, each with multiple teeth.
These prior art cutters suffer from various disadvantages, including low cutting rates, clogging, substantial maintenance downtime, high construction cost, and the necessity for a dedicated weed cutting watercraft. In addition, none of the prior art cutters known to applicant are capable of following bottom terrain changes. An aquatic vegetation cutter is needed which is simple in construction, easy to operate and maintain, adaptable to various water and plant conditions, and effective to achieve a high harvest rate.